1. Field of the Invention
The invention in general pertains to a method of disposing of the residue from the production of dialkyl and diaryl phosphorochloridothionate in an environmentally safe manner.
2. Prior Art
The distillation residue formed when phosphorochloridothionates are produced, as for instance, by the method disclosed in U.S. Pat. No. 3,089,890 incorporated herein by reference, is essentially comprised of a plastic mass of undissolved sulfur, dissolved organophosphorous compounds and other undissolved compounds. The distillation residue, which is generally disposed of by hydrolysis on a batch basis, has a highly offensive odor and is, in addition, thermally unstable.
When phosphorochloridothionate is prepared on a batch basis, the distillation residue resulting therefrom is disposed of by draining it into cold agitated water in a hydrolyzing zone, and heating the mixture slowly to a temperature of from 90.degree.-120.degree. C. By this process, the residue is decomposed into gases. However, the decomposition gases are produced at very uneven rates. During the peak rates of gas production, the odorous decomposition gases produced require the use of large volumes of air and fuel to prevent the odorous gases from escaping air swept hydrolyzers and abatement facilities into the atmosphere. These gases can cause severe odor problems. The decomposition gases resulting from the hydrolysis of the residue from the production of dialkyl phosphorochloridothionate can comprise HCl, ROH RSH, H.sub.2 S, RCl, CS.sub.2 and RS.sub.x R, where R in an alkyl or aryl radical. The decomposition gases are generally burnt in an incinerator at from about 750.degree. C.-800.degree. C.
These gases contain from about 30 to 50 weight percent sulfur, and therefore, require large abatement facilities to effectively prevent the escape of polluting gases such as SO.sub.2, H.sub.2 S, RSH, etc. to the atmosphere. The use of large abatement facilities to adequately eliminate such pollution require high fuel consumption and concomitant high costs.
A prior art method for treating the residue from the production of dialkyl thiophosphoric acid chloride is disclosed in German patent application No. P 2617812, filed Apr. 23, 1976. The method comprises placing the residue in alkalyzed water having a temperature of about -10.degree. C. to about 50.degree. C. and a pH of at least 10 in the resulting mixture, and contacting the aqueous phase and/or solid phases of the mixture formed therein with nitric acid at an elevated temperature and at a pH of below 3, convert the residue into fertilizer and/or crystalline sulfur.
Also, there is disclosed in U.S. patent application Ser. No. 78,640, filed Sept. 26, 1979, a process of treating distillate residue from phosphorochloridothionate production by introducing the residue into agitated water to form a pumpable and storeable slurry which is then hydrolyzed in controllable amounts.
It is an object of the present invention to provide a method of hydrolyzing the distillation residue whereby the sulfur content of the evolved waste gases is substantially reduced. A further object of the invention is to provide a method of hydrolyzing the distillation residue in controllable amounts which would dispense with the need for costly abatement facilities.